It is proposed to continue support for the Scanning Transmission Electron Microscopy Resource at Brookhaven in order to provide for the efficient use of expensive instrumentation essential for progress in biological structure studies. An instrument similar to that introduced by Dr. A. V. Crewe has been constructed in the Biology Department of Brookhaven National Laboratory. The instrument is capable of observing single heavy atoms and frozen-hydrated specimens. The microscope has been in operation since July 1976 and available to users since November 1977. A committee composed of Brookhaven biologists and academic biologists has been formed to oversee the application of the microscope to the study of a variety of biological materials on a time-sharing basis. The application includes research proposals of considerable scope which are expected to expedite the evaluation of the microscope for biomedical research. The facility will also provide for experimental work in sample preparation, heavy atom labeling, image analysis and the possibility of new instrumental developments for electron microscopy. Access to the facility will continue to be open to all qualified biomedical scientists and will be regulated by a Users' Committee to promote its efficient function as a national resource in health-related research and training.